The present invention relates to substituted metallocenes and highly active supported catalyst systems which can advantageously be used in olefin polymerization, and to a process for their preparation and also to polymers which are prepared using the supported catalyst systems.
Processes for preparing polyolefins using soluble, homogeneous catalyst systems comprising a transition metal component of the metallocene type and a cocatalyst component of the type of an aluminoxane, a Lewis acid or an ionic compound are known. These catalysts have a high activity and give polymers and copolymers having a narrow molar mass distribution.
In polymerizations using soluble, homogeneous catalyst systems, heavy deposits are formed on reactor walls and the stirrer if the polymer is obtained as a solid. These deposits are formed by agglomeration of the polymer particles whenever metallocene and/or cocatalyst are present in dissolved form in the suspension. The deposits in the reactor systems quickly reach considerable thicknesses and have a high strength. They prevent heat exchange to the cooling medium and therefore have to be removed regularly. Such homogeneous catalyst systems cannot be used industrially in the liquid monomer or in the gas phase.
To avoid deposit formation in the reactor, supported catalyst systems in which the metallocene and/or the aluminum compound serving as cocatalyst is/are fixed on an inorganic support material have been proposed.
EP-A-0 576 970 discloses metallocenes and corresponding supported catalyst systems.
At industrially relevant polymerization temperatures of from 50xc2x0 C. to 80xc2x0 C., the supported catalyst systems give polymers, in particular polypropylenes, having melting points of at most 156xc2x0 C. Typical values for such systems are merely in the region of 150xc2x0 C. For many polymer applications, for example extrusion and injection molding, such products are not satisfactory in respect of hardness and mechanical strength.
It is an object of the present invention to provide supported etallocene catalysts which, owing to their high regiospecificity and stereospecificity, give polymers having a higher melting point under industrially relevant polymerization conditions and provide an environmentally friendly and economical process for preparing the polymers.
We have found that this object is achieved by a supported catalyst system comprising at least one specifically substituted metallocene, at least one cocatalyst, at least one passivated support and, if desired, at least one further additive component. According to the present invention, the catalyst system is prepared by mixing at least one specifically substituted metallocene, at least one cocatalyst and at least one passivated support.
As metallocene component of the catalyst system of the present invention, use is made of at least one compound of the formula I below, 
where
M1 is metal of group IVb of the Periodic Table of the Elements,
R1 and R2 are identical or different and are each a hydrogen atom, a C1-C10-alkyl group, a C1-C10-alkoxy group, a C6-C20-aryl group, a C6-C10-aryloxy group, a C2-C10-alkenyl group, an OH group, an NR122 group, where R12 is a C1-C10-alkyl group or C6-C14-aryl group, or a halogen atom,
R3, R4, R6, R7, R8 and also R3xe2x80x2, R4xe2x80x2, R6xe2x80x2, R7xe2x80x2 and R8xe2x80x2 are identical or different and are each a hydrogen atom, a hydrocarbon group which may be halogenated, linear, cyclic or branched, for example a C1-C10 -alkyl group, C2-C10-alkenyl group, C6-C20-aryl group, a C7-C40-arylalkyl group, a C7-C40-alkylaryl group or a C8-C40-arylalkenyl group, with the proviso that R3 and R3xe2x80x2 are not hydrogen, and
R5 and R5xe2x80x2 are identical or different and are each a C6-C40-aryl group which in the para position to the bonding position on the indenyl ring bears a substituent R13 
where x, y=0, 1 and x+y=0, 1 or 2, where the aromatic ring system x and/or the aromatic ring system y can also be linked to the radicals R6, R6, or R4, R4xe2x80x2, and R13 is a C2-C20-alkyl radical, a C2-C20-alkenyl radical, a C6-C24-aryl radical, a C7-C40-arylalkyl radical, a C7-C40-alkylaryl radical, a C8-C40-arylalkenyl radical, where the hydrocarbon radicals may also be halogenated or partially halogenated by fluorine, chlorine or bromine, xe2x80x94NR214, xe2x80x94PR214, xe2x80x94SR14, xe2x80x94OR14, xe2x80x94SiR314, xe2x80x94NR314 or xe2x80x94PR3 14, where R14 is as defined for R3,
R9 is a bridge 
xe2x80x83where
R10 and R11, even when bearing the same index, can be identical or different and are each a hydrogen atom, a halogen atom or a C1-C40-group such as a C1-C20-alkyl group, a C1-C10-fluoroalkyl group, a C1-C10-alkoxy group, a C6-C14-aryl group, a C6-C10-fluoroaryl group, a C6-C10-aryloxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C7-C40-alkylaryl group or a C8-C40-arylalkenyl group or R10 and R11 together with the atoms connecting them form one or more rings, z is an integer from zero to 18 and M2 is silicon, germanium or tin, and
R9 may also link two units of the formula I to one another.
The 4,5,6,7-tetrahydroindenyl analogues corresponding to the compounds I are likewise of importance.
In formula I, it is preferred that
M1 is zirconium, hafnium or titanium,
R1 and R2 are identical and are methyl or chlorine,
R3 and R3xe2x80x2, are identical or different and are each a hydrocarbon group which may be halogenated, linear, cyclic or branched, for example a C1-C10-alkyl group, C2-C10-alkenyl group or a C7-C40-alkylaryl group,
R9 is R10R11Sixe2x95x90, R10R11Gexe2x95x90, R10R11Cxe2x95x90 or xe2x80x94(R10R11C-CR10R11)xe2x80x94, where R10 and R11 are identical or different and are each a C1-C20-hydrocarbon group, in particular C1-C10-alkyl or C6-C14-aryl,
R5 and R5xe2x80x2 are preferably identical or different and are each a C6-C20-aryl group which in the para position to the bonding position to the indenyl ring bears a substituent R13, 
xe2x80x83where x, y=0, 1 and x+y=0, 1 or 2 and
R13 is a C2-C10alkyl radical, a C2-C10-alkenyl radical, a C6-C18-aryl radical, a C7-C20-arylalkyl radical, a C7-C20-alkylaryl radical, a C8-C20-arylalkenyl radical, where the hydrocarbon radicals may also be halogenated or partially halogenated by fluorine or chlorine, xe2x80x94NR214, xe2x80x94PR214, xe2x80x94SR14, xe2x80x94SiR314, xe2x80x94NR314 or xe2x80x94PR314, where R14 is as defined for R3.
In formula I, it is very particularly preferred that
M1 is zirconium,
R1 and R2 are identical and are methyl or chlorine, in particular chlorine,
R9 is R10R11Sixe2x95x90, R10R11Cxe2x95x90 or xe2x80x94(R10R11C-CR10R11)xe2x80x94, where R10 and R11 are identical or different and are hydrogen, phenyl, methyl or ethyl,
R4, R6, R7 and R8 and also R4xe2x80x2, R6xe2x80x2, R7xe2x80x2 and R8xe2x80x2 are hydrogen, and
R5 and R5xe2x80x2 are identical or different and are each a C6-C20-aryl group, in particular a phenyl, naphthyl or anthracenyl group, which in the para position to the bonding position to the indenyl ring bears a substituent R13, where R13 is an SiR314 radical, where R14 is as defined for R3 or is a branched C3-C10alkyl radical, a C2-C10-alkenyl radical or a branched C7-C20-alkylaryl radical, where the hydrocarbon radicals may also be halogenated or partially halogenated by fluorine or chlorine.
Preferred metallocene components of the catalyst system of the present invention are combinations of the following molecular fragments of the compound I
M1R1R2 is ZrCl2, Zr(CH3)2,
R3,R3xe2x80x2 are methyl, ethyl, isopropyl, isobutyl, n-butyl, s-butyl,
R4,R8,R4xe2x80x2,R8xe2x80x2 are hydrogen,
R6,R7,R6xe2x80x2,R7xe2x80x2 are hydrogen, C1-C4-alkyl, C6-C10-aryl,
R5 and R5 xe2x80x2 are p-isopropylphenyl, p-tert-butylphenyl, p-s-butyl-phenyl, p-cyclohexyl, p-trimethylsilylphenyl, p-adamantylphenyl, p-(F3C)3C-phenyl
R9 is dimethylsilanediyl, dimethylgermanediyl, ethylidene, 1-methylethylidene, 1,1-dimethylethylidene, 1,2-dimethylethylidene, 1,1,2,2-tetramethylethylidene, dimethylmethylidene.
Particularly preferred metallocene compounds of the catalyst system of the present invention are thus the following compounds I dimethylsilanediylbis(2-methyl-4-(p-isopropylphenyl)indenyl)ZrCl2 dimethylsilanediylbis(2-methyl-4-(p-tert-butylphenyl)indenyl)ZrCl2 dimethylsilanediylbis(2-methyl-4-(p-s-butylphenyl)indenyl)ZrCl2 dimethylsilanediylbis(2-methyl-4-(p-cyclohexylphenyl)indenyl)ZrCl2 dimethylsilanediylbis(2-methyl-4-(p-trimethylsilylphenyl)-indenyl)ZrCl2 dimethylsilanediylbis(2-methyl-4-(p-adamantylphenyl)indenyl)ZrCl2 dimethylsilanediylbis(2-methyl-4-(p-tris(trifluoromethyl)methyl-phenyl)indenyl)ZrCl2 and the corresponding dimethylgermanediyl-, ethylidene-, 1-methylethylidene-, 1,1-dimethylethylidene-, 1,2-dimethyl-ethylidene-, 1,1,2,2-tetramethylethylidene- and dimethylmethylidene-bridged compounds.
Particularly preferred metallecene components are also the corresponding 2-ethyl-, 2-isopropyl-, 2-isobutyl-, 2-n-butyl-, 2-s-butyl-substituted homologues of the abovementioned compounds I. Methods for preparing metallocenes of the formula I are described, for example, in Journal of Organometallic Chem. 288 (1985) 63-67 and in the documents cited therein.
The catalyst system of the present invention preferably further comprises at least one cocatalyst.
The cocatalyst component which may be present according to the present invention in the catalyst system comprises at least one compound of the type of an aluminoxane or a Lewis acid or an ionic compound which reacts with a metallocene to convert the latter into a cationic compound.
As aluminoxane, preference is given to using a compound of the formula II
(R AIO)nxe2x80x83xe2x80x83(II).
Aluminoxanes may be, for example, cyclic as in formula III 
or linear as in formula IV 
or of the cluster type as in formula V, as described in recent literature, cf. JACS 117 (1995), 6465-74, Organometallics 13 (1994), 2957-2969. 
The radicals R in the formulae (II), (III), (IV) and (V) can be identical or different and are each a C1-C20-hydrocarbon group such as a C1-C6-alkyl group, a C6-C18-aryl group, benzyl or hydrogen and p is an integer from 2 to 50, preferably from 10 to 35.
Preferably, the radicals R are identical and are methyl, isobutyl, n-butyl, phenyl or benzyl, particularly preferably methyl.
If the radicals R are different, they are preferably methyl and hydrogen, methyl and isobutyl or methyl and n-butyl, with hydrogen, isobutyl or n-butyl preferably being present in a proportion of from 0.01 to 40% (number of radicals R).
The aluminoxane can be prepared in various ways by known methods. One of the methods is to react an aluminum-hydrocarbon compound and/or a hydridoaluminum-hydrocarbon compound with water, which may be gaseous, solid, liquid or bound as water of crystallization, in an inert solvent such as toluene. To prepare an aluminoxane having different alkyl groups R, two different trialkylaluminums (AlR3+AlRxe2x80x23) corresponding to the desired composition and reactivity are reacted with water, cf. S. Pasynkiewicz, Polyhedron 9 (1990) 429 and EP-A-0 302 424.
Useful metallocenes of the formula I are those which are disclosed in the German Patent Application 197 094 02.3 on page 78, line 21 to page 100, line 22 and in the German Patent Application 197 135 46.3 on page 78, line 14 to page 103, line 22, which are hereby expressly incorporated by reference.
Regardless of the method of preparation, all aluminoxane solutions have in common a variable content of unreacted aluminum starting compound which is present in free form or as adduct.
As Lewis acid, preference is given to using at least one organoboron or organoalumninum compound containing C1-C20-groups, such as branched or unbranched alkyl or haloalkyl, eg. methyl, propyl, isopropyl, isobutyl or trifluoromethyl, unsaturated groups such as aryl or haloaryl, eg. phenyl, tolyl, benzyl groups, p-fluorophenyl, 3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl, 3,4,5-trifluorophenyl and 3,5-di(trifluoromethyl)phenyl.
Preferred Lewis acids are trimethylaluminuin, triethylaluminum, truisobutylaluminum, tributylaluminum, trifluoroborane, triphenylborane, tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane, tris(4-fluoromethylphenyl)borane, tris(penta-fluorophenyl)borane, tris(tolyl)borane, tris(3,5-dimethyl-phenyl)borane, tris(3,5-difluorophenyl)borane and/or tris (3,4,5-trifluorophenyl)borane.
Particular preference is given to tris(pentafluorophenyl)borane.
As ionic cocatalysts, preference is given to using compounds which contain a non-coordinating anion such as tetrakis(pentafluorophenyl)borate, tetraphenylborate, SbF6xe2x88x92, CF3SO3 xe2x88x92 or ClO4xe2x88x92. Cationic counterions used a re Lewis bases such as methylamine, aniline, dimethylamine, diethylamine, N-methylaniline, diphenylamine, N,N-dimethylaniline, trimethylamine, triethylamine, tri-n-butylamine, methyldiphenylamine, pyridine, p-bromo-N,N-dimethylaniline, p-nitro-N,N-dimethylaniline, triethylphosphine, triphenylphosphine, diphenylphosphine, tetrahydrothiophene and triphenylcarbeniuyo.
Ionic compounds which can be used according to the present invention are triethylammonium tetra(phenyl)borate, tributylammonium tetra(phenyl)borate, trimethylammonium tetra(tolyl)borate, tributylammonium tetra(tolyl)borate, tributylammonium tetra(pentafluorophenyl)borate, tributylammonium tetrak(spentaffluorophenyl) a luminate, tripropylammonium tetra(dimet hylphenyl)bborate, tributylammonium tetra(trifluoromethylphenyl )borate, tributylammonium tetra(4-fluorophenyl)borate, N,N-dimethylanilinium tetral(phenyld)borate, N,N-diethylanilinium tetra(phenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)aluminate, di(propyl)ammonium tetrakis(pentafluorophenyl)borate, di(cyclohexyl)ammonium tetrakist(pentafluorophenyl)borate, triphenylphosphonium tetrakis(phenyl)borate, triethylphosphonium tetrakis(phenyl)borate, diphenylphosphonium tetrakis(phenyl)borate, tri(methylphenyl)phosphonium tetrakis (phenyl)borate, tri(dimethylphenyl)phosphonium tetrakis(phenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl) aluminate, triphenylcarbenium tetrakis(phenyl)aluminate, ferrocenium tetrakis(pentafluorophenyl)borate and/or ferrocenium tetrakis(pentafluorophenyl)aluminate.
Preference is given to triphenylcarbenium tetrakis(pentafluorophenyl)borate and/or N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate.
It is also possible to use mixtures of at least one Lewis acid and at least one ionic compound.
Other useful cocatalyst components are likewise borane or carborane compounds such as 7,8-dicarbaundecaborane(13), undecahydrido-7,8-dimethyl-7,8-dicarbaundecaborane, dodecahydrido-1-phenyl-1,3-dicarbanonaborane, tri(butyl)ammoniumun decahydrido-8-ethyl-7,9-dicarbaundecaborate, 4-carbanonaborane(14), bis(tri(butyl)ammonium)nonaborate, bis(tri(butyl)ammonium)undecaborate, bis(tri(butyl)ammonium)dodecaborate, bis(tri(butyl)ammonium)decachlorodecaborate, tri(butyl)ammonium 1-carbadecaborate, tri(butyl)ammonium 1-carbadodecaborate, tri(butyl)ammonium 1-trimethylsilyl-1-carbadecaborate, tri(buyl)ammonium bis(nonahydrido-1, 3-dicarbanonaborato)cobaltate(III), tri(butyl)ammonium bis(undecahydrido-7,8-dicarbaundecaborato)ferrate(III).
The support component of the catalyst system of the present invention can be any organic or inorganic, inert solid, in particular a porous support such as talc, inorganic oxides and finely divided polymer powders, polyolefins.
Suitable inorganic oxides are found in Groups 2, 3, 4, 5, 13, 14, 15 and 16 of the Periodic Table of the Elements. Preferred oxides for supports are silicon dioxide, aluminum oxide and also mixed oxides of the two elements and the corresponding oxide mixtures. Other inorganic oxides which can be used alone or in combination with the preferred oxidic supports mentioned are MgO, ZrO2, TiO2 or B2O3.
The support materials used have a specific surface area in the range from 10 to 1000 m2/g, a pore volume in the range from 0.1 to 5 ml/g and a mean particle size of from 1 to 500 xcexcm. Preference is given to supports having a specific surface area in the range from 50 to 500 xcexcm, a pore volume in the range from 0.5 to 3.5 ml/g and a mean particle size in the range from 5 to 350 xcexcm. Particular preference is given to supports having a specific surface area in the range from 200 to 400 m2/g, a pore volume in the range from 0.8 to 3.0 ml/g and a mean particle size of from 10 to 200 xcexcm.
If the support material used naturally has a low moisture content or residual solvent content, dehydration or drying before use can be omitted. If this is not the case, as when using silica gel as support material, dehydration or drying is advisable. Thermal dehydration or drying of the support material can be carried out under reduced pressure with simultaneous inert gas blanketing (nitrogen). The drying temperature is in the range from 100xc2x0 C. to 1000xc2x0 C., preferably from 200xc2x0 C. to 800xc2x0 C. The pressure is not critical in this case. The duration of the drying process can be from 1 to 24 hours. Shorter or longer drying times are possible, provided that equilibrium with the hydroxyl groups on the support surface can be established under the conditions selected which normally takes from 4 to 8 hours.
Dehydration or drying of the support material can also be carried out by chemical means, by reacting the adsorbed water and the hydroxyl groups on the surface with suitable passivating agents. Reaction with the passivating reagent can convert the hydroxyl groups completely or partially into a form which leads to no adverse interaction with the catalytically active centers. Suitable passivating agents are silicon halides and silanes, eg. silicon tetrachloride, chlorotrimethylsilane or dimethylaminotrichlorosilane, or organometallic compounds of aluminum, boron and magnesium, eg. trimethylaluminum, triethylaluminum, triisobutylaluminum, triethylborane or dibutylmagnesium. The chemical dehydration or passivation of the support material is carried out by reacting, with-exclusion of air and moisture, a suspension of the support material in a suitable solvent with the passivating reagent in pure form or dissolved in a suitable solvent. Suitable solvents are aliphatic or aromatic hydrocarbons such as pentane, hexane, heptane, toluene or xylene. The passivation is carried out at from 25xc2x0 C. to 120xc2x0 C., preferably from 50xc2x0 C. to 70xc2x0 C. Higher and lower temperatures are possible. The duration of the reaction is from 30 minutes to 20 hours, preferably from 1 to 5 hours. After the chemical dehydration is complete, the support material is isolated by filtration under inert conditions, washed one or more times with suitable inert solvents as described above and subsequently dried in a stream of inert gas or under reduced pressure.
Organic support materials such as finely divided polyolefin powders, eg. polyethylene, polypropylene or polystyrene, can also be used and should, before use, likewise be freed of adhering moisture, solvent residues or other impurities by means of appropriate purification and drying operations.
To prepare the supported catalyst system, at least one of the above-described metallocene components is brought into contact in a suitable solvent with at least one cocatalyst component, preferably giving a soluble reaction product, an adduct or a mixture.
The composition obtained in this way is then mixed with the dehydrated or passivated support material, the solvent is removed and the resulting supported metallocene catalyst system is dried to ensure that the solvent is completely or mostly removed from the pores of the support material. The supported catalyst is obtained as a free-flowing powder.
A process for preparing a free-flowing and, if desired, prepolymerized supported catalyst system comprises the following steps:
a) preparing a metallocene/cocatalyst mixture in a suitable solvent or suspension medium, where the metallocene component has one of the above-described structures,
b) applying the metallocene/cocatalyst mixture to a porous, preferably inorganic, dehydrated support,
c) removing the major part of solvent from the resulting mixture,
d) isolating the supported catalyst system and
e) if desired, prepolymerizing the resulting supported catalyst system with one or more olefinic monomer(s) to obtain a prepolymerized supported catalyst system.
Preferred solvents for the preparation of the metallocene/cocatalyst mixture are hydrocarbons and hydrocarbon mixtures which are liquid at the reaction temperature selected and in which the individual components preferably dissolve. The solubility of the individual components is, however, not a prerequisite as long as it is ensured that the reaction product of metallocene and cocatalyst components is soluble in the solvent selected. Suitable solvents are alkanes such as pentane, isopentane, hexane, heptane, octane and nonane, cycloalkanes such as cyclopentane and cyclohexane and aromatics such as benzene, toluene, ethylbenzene and diethylbenzene. Very particular preference is given to toluene.
The amounts of aluminoxane and metallocene used in the preparation of the supported catalyst system can be varied within a wide range. Preference is given to using a molar ratio of aluminum to transition metal in the metallocene of from 10:1 to 1000:1, very particularly preferably from 50:1 to 500:1. In the case of methylaluminoxane, preference is given to using 30% strength toluene solutions, but the use of 10% strength solutions is also possible.
For the preactivation, the metallocene in the form of a solid is dissolved in a solution of the aluminoxane in a suitable solvent. It is also possible to dissolve the metallocene separately in a suitable solid and subsequently to combine this solution with the aluminoxane solution. Preference is given to using toluene. The preactivation time is from 1 minute to 200 hours. The preactivation can take place at room temperature of 25xc2x0 C. The use of higher temperatures can in individual cases reduce the preactivation time required and give an additional increase in activity. Elevated temperatures in this case refer to a range from 50xc2x0 C. to 100xc2x0 C.
The preactivated solution or the metallocene/cocatalyst mixture is subsequently combined with an inert support material, usually silica gel, which is in the form of a dry powder or as a suspension in one of the abovementioned solvents. The support material is preferably used as powder. The order of addition is unimportant. The preactivated metallocene/cocatalyst solution or the metallocene/cocatalyst mixture can be added to the initially charged support material, or else the support material can be introduced into the initially charged solution.
The volume of the preactivated solution or the metallocene/cocatalyst mixture can exceed 100% of the total pore volume of the support material used or else be up to 100% of the total pore volume.
The temperature at which the preactivated solution or the metallocene/cocatalyst mixture is brought into contact with the support material can vary within the range from 0xc2x0 C. to 100xc2x0 C. Lower or high temperatures are, however, also possible.
Subsequently, the solvent is completely or mostly removed from the supported catalyst system; during this procedure, the mixture can be stirred and, if desired, also heated. Preferably, both the visible proportion of the solvent and the proportion in the pores of the support material are removed. The removal of the solvent can be carried out in a conventional way using reduced pressure and/or purging with inert gas. During the drying process, the mixture can be heated until the free solvent has been removed, which usually takes from 1 to 3 hours at a preferred temperature of from 30xc2x0 C. to 60xc2x0 C. The free solvent is the visible proportion of solvent in the mixture. For the purposes of the present invention, residual solvent is the proportion present in the pores.
As an alternative to complete removal of the solvent, the supported catalyst system can also be dried only as far as a particular residual solvent content, with the free solvent having been completely removed. Subsequently, the supported catalyst system can be washed with a low-boiling hydrocarbon such as pentane or hexane and dried again.
The supported catalyst system prepared according to the present invention can be used either directly for the polymerization of olefins or be prepolymerized with one or more olefinic monomers prior to use in a polymerization process. The procedure for the prepolymerization of supported catalyst systems is described in WO 94/28034.
As additive, it is possible to add, during or after the preparation of the supported catalyst system, a small amount of an olefin, preferably an xcex1-olefin such as styrene or phenyl-dimethylvinylsilane as activity-increasing component or an antistatic, as described in U.S. Ser. No. 08/365,280. The molar ratio of additive to metallocene component compound I is preferably from 1:1000 to 1000:1, very particularly preferably from 1:20 to 20:1.
The present invention also provides a process for preparing a polyolefin by polymerization of one or more olefins in the presence of the catalyst system of the present invention comprising at least one transition metal component of the formula I. For the purposes of the present invention, the term polymerization refers to both homopolymerization and copolymerization.
Preference is given to polymerizing olefins of the formula Rmxe2x80x94CHxe2x95x90CHxe2x80x94Rn, where Rm and Rn are identical or different and are each a hydrogen atom or a radical having from 1 to 20 carbon atoms, in particular from 1 to 10 carbon atoms, and Rm and Rn together with the atoms connecting them can form one or more rings.
Suitable olefins are 1-olefins having from 2 to 40, preferably from 2 to 10, carbon atoms, eg. ethene, propene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene, styrene, dienes such as 1,3-butadiene, 1,4-hexadiene, vinylnorbornene, norbornadiene, ethylnorbornadiene and cyclic olefins such as norbornene, tetracyclododecene or methylnorbornene. In the process of the present invention, preference is given to homopolymerizing propene or ethene or copolymerizing propene with ethene and/or one or more 1-olefins having from 4 to 20 carbon atoms, eg. hexene, and/or one or more dienes having from 4 to 20 carbon atoms, eg. 1,4-butadiene, norbornadiene, ethylidenenorbornene or ethylnorbornadiene. Suitable copolymers are ethene-propene copolymers or ethene-propene-1,4-hexadiene terpolymers.
The polymerization is carried out at from xe2x88x9260xc2x0 C. to 300xc2x0 C., preferably from 50xc2x0 C. to 200xc2x0 C., very particularly preferably from 50xc2x0 C. to 80xc2x0 C. The pressure is from 0.5 to 2000 bar, preferably from 5 to 64 bar.
The polymerization can be carried out in solution, in bulk, in suspension or in the gas phase, continuously or batchwise, in one or more stages.
The catalyst system prepared according to the present invention can be used as sole catalyst component for the polymerization of olefins having from 2 to 20 carbon atoms, or preferably in combination with at least one alkyl compound of elements of Main Groups I to III of the Periodic Table, for example an aluminum alkyl, magnesium alkyl or lithium alkyl or an aluminoxane. The alkyl compound is added to the monomer or suspension medium and serves to free the monomer of substances which can impair the catalytic activity. The amount of alkyl compound added depends on the quality of the monomers used.
As molar mass regulator and/or to increase the activity, hydrogen is added if required.
In the polymerization, it is also possible to meter an antistatic into the polymerization system, either together with or separately from the catalyst system used.
The polymers prepared using the catalyst system of the present invention display a uniform particle morphology and contain no fines. No deposits or caked material are obtained in the polymerization using the catalyst system of the present invention.
The catalyst system of the present invention gives polymers such as polypropylene having extraordinarily high stereospecificity and regiospecificity.
Particularly characteristic for the stereospecificity and regiospecificity of polymers, in particular polypropylene, is the triad tacticity (TT) and the proportion of 2-1-inserted propene units (RI), which can be determined from the 13C NMR spectra.
The 13C NMR spectra are measured in a mixture of hexachlorobutadiene and d2-tetrachloroethane at elevated temperature, eg. 365 K. All 13C NMR spectra of the polypropylene samples measured are calibrated on the basis of the resonance signal of d2-tetrachloro-ethane (xcex4=73.81 ppm).
The triad tacticity of the polypropylene is determined from the methyl resonance signals in the 13C NMR spectrum from 23 to 16 ppm, cf. J. C. Randall, Polymer Sequence Determination: Carbon 13 NMR Method, Academic Press New York 1978, A. Zambelli, P. Locatelli, G. Bajo, F. A. Bovey, Macromolucules 8 (1975), 687-689, H. N. Cheng, J. A. Ewen, Makromol. Chem. 190 (1989), 1931-1943. Three successive 1-2-inserted propene units whose methyl groups are arranged on the same side in the xe2x80x9cFischer projection xe2x80x9d are referred to as mm triads (xcex4=21.0 ppm to 22.0 ppm). If only the second methyl group of the three successive propene units points to the other side, the sequence is referred to as an rr triad (xcex4=19.5 ppm to 20.3 ppm) and if only the third methyl group of the three successive propene units points to the other side, the sequence is referred to as an mr triad (xcex4=20.3 ppm to 21.0 ppm). The triad tacticity is calculated according to the following formula
TT (%)=mm/(mm+mr+rr)xc3x97100
If a propene unit is inserted in reverse into the growing polymer chain, this is referred to as a 2 1 insertion, cf. T. Tsutsui, N. Ishimaru, A. Mizuno, A. Toyota, N. Kashiwa, Polymer 30, (1989), 1350-56. The following different structural arrangements are possible: 
The proportion of 2-1-inserted propene units (RI) can be calculated according to the following formula:
RI (%) 0.5 Ia,xcex2(Ia,a+Ia,xcex2+Ia,d)xc3x97100,
where
Ia,a is the sum of the intensities of the resonance signals at xcex4=41.84, 42.92 und 46.22 ppm,
Ia,xcex2 is the sum of the intensities of the resonance signals at xcex2=30.13, 32.12, 35.11 and 35.57 ppm and
Ia,d is the intensity of the resonance signal at xcex4=37.08 ppm.
A particularly high regiospecificity also gives a particularly high melting point of the polymer, in particular the isotactic polypropylene. The isotactic polypropylene which has been prepared using the catalyst system of the present invention has a proportion of 2-1-inserted propene units RI less than 0.5% at a triad tacticity TT greater than 98.0% and a melting point  greater than 156xc2x0 C., and the Mw/Mn of the polypropylene prepared according to the present invention is from 2.5 to 3.5.
The copolymers which can be prepared using the catalyst system of the present invention have a significantly higher molar mass compared to the prior art. At the same time, such copolymers can be prepared using the catalyst system of the present invention at a high productivity and at industrially relevant process parameters without deposit formation.
The polymers prepared by the process of the present invention are suitable, in particular, for producing strong, hard and stiff shaped products such as fibers, filaments, injection-molded parts, films, sheets or large hollow bodies such as pipes.